Creating a Deployment in Kubernetes using YAML

 

You'll learn how real applications are deployed, configured, scaled, updated, and healed automatically.

What is a Deployment?

A Deployment is a Kubernetes resource used to manage and deploy applications. It ensures that the desired number of Pods are running and provides features like scaling, rolling updates, and self-healing.

Deployment YAML Example

Create a file named deployment.yaml:

apiVersion: apps/v1

kind: Deployment

metadata:

  name: nginx-deployment

spec:

  replicas: 3

  selector:

    matchLabels:

      app: nginx

  template:

    metadata:

      labels:

        app: nginx

    spec:

      containers:

      - name: nginx

        image: nginx:latest

        ports:

        - containerPort: 80

Understanding the YAML

apiVersion - Specifies the API version used by the Deployment.

apiVersion: apps/v1

kind - Defines the resource type. example (Pod, Deployment, Services)

kind: Deployment

metadata - Gives the deployment a name.

metadata:

  name: nginx-deployment

replicas - Creates desired no of identical Pods.

replicas: 3

selector - Used to identify the Pods managed by this Deployment. (Selector identifies which Pods are managed by the Deployment.)

selector:

  matchLabels:

    app: nginx

template - Represents the Pod template. (Create Pods with label app: nginx and run the nginx container.)

template:

container image - Specifies the container image to use.

image: nginx:latest

Create Deployment

kubectl apply -f deployment.yaml

Verify Deployment

kubectl get deployments

kubectl get rs

kubectl get pods

Scale Deployment (Increase replicas from 3 to 5)

kubectl scale deployment nginx-deployment --replicas=5

kubectl get pods

Update Deployment

Update image version - kubectl set image deployment/nginx-deployment nginx=nginx:1.26

Check rollout status - kubectl rollout status deployment/nginx-deployment

Rollback Deployment

View rollout history - kubectl rollout history deployment nginx-deployment

Rollback - kubectl rollout undo deployment nginx-deployment

Self-Healing Example (Delete a Pod)

kubectl delete pod <pod-name>

Kubernetes automatically creates a new Pod to maintain the desired replica count.